An international human rights group has called on the Vietnamese government to shut down scores of drug rehabilitation centers and release tens of thousands of people it says are being held against their will and compelled to endure forced labor and torture.

The New York-based Human Rights Watch (HRW), in a report released Wednesday, said the government-run drug detention centres are little more than forced labor camps where drug users work long hours for little or no pay.

Thousands of detainees, including women and children, are made to work up to 10 hours a day doing unhealthy and tedious work such as shelling cashews, it alleges. The oil from the nuts is caustic and can burn the skin. Other detainees are forced to do farming, work in construction, sew garments and do other menial labor. Those who refuse to work are subjected to torture and deprived of food and water, it says.

Vietnam is the world’s largest exporter of processed cashews and the main supplier to the United States.

The 126-page report, “The Rehab Archipelago,” also alleges that Western governments, the United Nations, the World Bank and other international donors may be indirectly facilitating these alleged abuses through drug rehabilitation and HIV support programs linked to the centers.

“Forced labor is not treatment, and profit-making is not rehabilitation,” said Joe Amon, HRW’s health and human rights director. “Donors should recognize that building the capacity of these centers perpetuates injustice, and companies should make sure their contractors and suppliers are not using goods from these centers.”

According to government figures cited in the report, more than 40,000 people are currently detained in 123 drug-rehabilitation centers across Vietnam, up from only 56 just a decade ago. HRW interviewed 34 former detainees as part of research for the report. Most of those in the centers are young men battling heroin addiction.

“People who are dependent on drugs in Vietnam need access to community-based, voluntary treatment,” Amon said. “Instead, the government is locking them up, private companies are exploiting their labor, and international donors are turning a blind eye to the torture and abuses they face.”

The Vietnamese government denies the allegations, saying “compulsory rehabilitation” is undertaken in the interests of the individual and the wider community.

“[The report]… is groundless, distorting Vietnam’s rehabilitation reality with ill intention,” the Vietnamese Ministry of Foreign Affairs Spokesperson Nguyen Phuong Nga said. “Work-based therapy, which is a part of [the] rehabilitation process, is aimed at helping drug users improve their health, life and professional skills, and understand [the] value of working and responsibility for family and society.”

She said the centers had shown that compulsory rehabilitation is “humane, effective and beneficial for drug users, community and society.

But the former detainees HRW interviewed disagree, claiming they suffered health problems from the work and were tortured if they tried to refuse or escape. “I would sometimes inhale the dust from the skins, and that would make me cough,” one man is quoted in the report as saying. “If the fluid from the hard outer husk got on your hands, it made a burn.”

Detainees are commonly held in the centres after being detained by police or taken there by family members. HRW says many are incarcerated in the centers without due process. Many are kept working at them for years without pay and with no hope of leaving, with their detention arbitrarily extended by center management or changes in government policy.

One former detainee spoke of being tortured after he was caught trying to escape. “First they beat my legs so that I couldn’t run off again… [Then] they shocked me with an electric baton [and] kept me in the punishment room for month,” said Quynh Lu. HRW says what is taking place in the centers constitutes torture under international law.

HRW has urged all international donors active in Vietnam, including UN agencies, to publicly call for the centers to be closed and have all the detainees released. The UN in Vietnam says it is concerned by the report and has been working with the Vietnamese government to try and widen the use of community-based treatment for drug users.

“The UN in Vietnam has consistently advocated against the use of the centers since they violate the right to due process and are ineffective as treatment,” said Eamonn Murphy, the UN resident coordinator in Vietnam. “The UN in Vietnam promotes community-based alternatives for drug dependence treatment services and urges an end to the compulsory detention practice of drug users.”

Murphy said the UN in Vietnam had not received any reports of torture in detention centers prior to the publication of the HRW report. “The UN in Vietnam is very concerned about the issues raised and is asking for the assistance the Office of the United Nations High Commissioner for Human Rights (OHCHR), to respond,” he said.

In a separate response, the United Nations Office on Drugs and Crime (UNODC) said it was concerned by the allegations but also pointed out the positive steps being made through its ongoing work with the Vietnamese government, such as commitments to expand a methadone maintenance treatment programs for heroin users to 80,000 users by 2015.

“There are a number of factors which make the compulsory treatment approach the one which has been adopted and maintained by governments and citizens of this region,” said Gary Lewis, the UNODC’s regional representative for East Asia and the Pacific. “In order to change these perspectives, it will be necessary to engage with our counterparts and provide evidence of a better alternative. And this is what UNODC—and other UN agencies—are trying to do.”

The report is also potentially embarrassing for foreign companies doing business in Vietnam and HRW has called on companies to thoroughly scrutinize the sourcing of all their products in the country. One of the companies named in the report, Switzerland-based Vestergaard Frandsen SA, has already cut ties with five of its subcontractors after HRW brought the issue to its attention. HRW welcomed the move, saying the company “responded to the allegations brought to its attention with appropriate seriousness and speed.”

However, it stressed that foreign companies doing business in Vietnam need to have effective systems in place to proactively detect and respond to abuse on their own, rather than responding to outside reports.